In conventional diesel engines, air is drawn into a combustion chamber during an intake stroke by opening one or more intake valves. Then, during the subsequent compression stroke, the intake valves are closed, and a reciprocating piston of the combustion chamber compresses the gasses admitted during the intake stroke, increasing the temperature of the gasses in the combustion chamber. Fuel is then injected into the hot, compressed gas mixture in the combustion chamber, resulting in combustion of the fuel. Thus, in a diesel engine, the fuel may combust with the air in the combustion chamber due to the high temperature of the air, and may not be ignited via a spark plug as in a gasoline engine. The combusting air-fuel mixture pushes on the piston, driving motion of the piston, which is then converted into rotational energy of a crankshaft.
However, the inventors herein have recognized potential issues with such diesel engines. As one example, diesel fuel may not mix evenly with the air in the combustion chamber, leading to the formation of dense fuel pockets in the combustion chamber. These dense regions of fuel may produce soot as the fuel combusts. As such, conventional diesel engines include particulate filters for reducing soot and other particulate matter in their emissions. However, such particulate filters lead to increased cost and increased fuel consumption.
In one example, the issues described above may be addressed by a cooling passage for an internal combustion engine, the cooling passage positioned exterior to a cylinder bore and wherein the cooling passage may be coupled to the cylinder bore at a first opening for receiving gasses from the cylinder bore, and where the cooling passage may be further coupled to the cylinder bore at a second opening for returning the gasses received from the cylinder bore via the first opening, back to the cylinder bore. In this way, a temperature of the gasses in the combustion chamber with which injected fuel initially mixes may be reduced by flowing the gasses out of the combustion chamber. By reducing the temperature of the gasses with which the injected fuel initially mixes, and amount of time and/or a distance over which the injected fuel and air mix prior to combustion may be increased, thus reducing particulate and/or soot production.
In another representation, the issues described above may be addressed by a method comprising admitting intake gasses from an intake manifold into a combustion chamber during an intake stroke via opening one or more intake valves, and flowing at least a portion of the intake gasses out of the combustion chamber and into a mixing passage fluidly coupled to the combustion chamber during a compression stroke. By flowing the intake gasses out of the combustion chamber during the compression stroke a temperature of the gasses with which injected fuel initially mixes may be reduced. By increasing cooling of the gasses with which injected fuel initially mixes, an amount of air and fuel mixing prior to combustion may be increased. Thus, the lift-off length and/or air entrainment of fuel may be increased, and thus soot production may be reduced during the combustion cycle.
In another representation, the issues described above may be addressed by an engine comprising a combustion chamber and a heat dissipation conduit, where the heat dissipation conduit may be fluidly coupled to the combustion chamber and positioned exterior to the combustion chamber for flowing gasses in the combustion chamber out and away from the combustion chamber towards a fuel injector. In the above example engine, the heat dissipation conduit may be coupled at a first end to a fire deck of the combustion chamber, where the first end may form a first opening in the fire deck that provides fluidic communication between the combustion chamber and the heat dissipation conduit.
In another representation, an engine may comprise a combustion chamber, an intake manifold fluidly communicating with the combustion chamber via one or more intake valves, an exhaust manifold fluidly communicating with the combustion chamber via one or more exhaust valves, a fuel injector, and a mixing passage coupled and open to the combustion chamber for receiving gasses from the combustion chamber, the mixing passage positioned exterior to the combustion chamber. In some examples, the mixing passage may include a cooled air conduit and a fuel spray conduit, where the cooled air conduit may be coupled at a first end to the combustion chamber, and at an opposite second end to the fuel spray conduit for directing gasses from the combustion chamber to the fuel spray conduit. The fuel spray conduit may be coupled at a first end to the combustion chamber, and at an opposite second end to the fuel injector for directing fuel injected by the fuel injector from the fuel injector to the combustion chamber via the second opening.
In this way, a temperature of gasses in the combustion chamber with which injected fuel initially mixes may be reduced by flowing the gasses out of the combustion chamber. The gasses may dissipate heat to the surrounding environment, such as to a cylinder head and/or ambient air. By reducing the temperature of the gasses with which the injected fuel initially mixes, and amount of time and/or a distance over which the injected fuel and air mix prior to combustion may be increased, thus leading to an increased amount of air entrained by the fuel prior to combustion. A more thorough and even mixing of the fuel and air may thus lead to reduced particulate matter and/or soot production. In this way, the frequency at which a particulate matter filter is regenerated may be reduced, thus reducing fuel consumption. In some examples, soot and particulate matter may be reduced to sufficiently low levels such that a particulate matter filter may not be included in the engine, thus reducing the cost of the engine.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.